Messenger activity has been detected by in vitro translation and specific immunoprecipitation, for the capsid polypeptide (SCV-Pl) and the presumed intracellular precursor (M-Pl, 32k. daltons) of the exocellular toxin (tox-l, 12 k. daltons) produced by killer strains of the yeast, Saccharomyces cerevisiae. Messenger will be quantitated throughout the yeast cell cycle and will be characterized for 5' caps and 3' polyadenylation. Maturation of M-Pl will be studied using membrane preparations.